
// Copyright (C) 2012 Luca Piccioni
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//  
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//  
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

using System;
using System.Collections.Generic;
using System.Text;

namespace Derm.Render
{
	/// <summary>
	/// Directional light.
	/// </summary>
	public class DirectionalLight : Light
	{
		#region Directional Light Information

		/// <summary>
		/// 
		/// </summary>
		[RenderObjectUniformAttribute("Position")]
		public Vertex4f Position = new Vertex4f(0.0f, 0.0f, 0.0f, 0.0f);

		/// <summary>
		/// 
		/// </summary>
		[RenderObjectUniformAttribute("Direction")]
		public Vertex3f Direction = Vertex3f.UnitZ;

		/// <summary>
		/// 
		/// </summary>
		[RenderObjectUniformAttribute("HalfVector")]
		public Vertex3f HalfVector = Vertex3f.UnitZ;

		#endregion

		#region Light Overrides

		internal override void UpdateViewState(ModelMatrix lightMatrix, Vertex3f eyePosition, Vertex3f viewVector)
		{
			Matrix3x3 lightRotationMatrix = new Matrix3x3(lightMatrix, 3, 3);

			// Direction light
			Position.W = 0.0f;
			// Light direction
			Direction = lightRotationMatrix * Vertex3f.UnitZ;
			Direction.Normalize();
			// Half vector
			HalfVector = Direction + viewVector;
			HalfVector.Normalize();
		}

		#endregion
	}
}
